Sample Analysis Approaches on Mars Subsurface Missions

As Mars exploration objectives increasingly consider and prioritize subsurface missions for both scientific and human exploration goals, we share a renewed opportunity and requirement to deploy powerful analytical tools that are prepared for unfamiliar conditions and compositions at depth. Analysis of drill samples from this "buried Mars" could lead to significant advances in astrobiology and geochemistry. Below the dessicated and radiation-baked uppermost meter, across much of the surface, we may increasingly encounter well-preserved complex organic compounds that could point to the emergence of life on ancient Mars. Liquid-water containing samples could additionally represent realistic targets to seek the signs of extant life.

The near subsurface (up to 10 m) could, and should, continue to be explored by coupling long-duration rovers with significant (multi-meter) sampling drills and focused, miniature analytical payloads. For example, existing highly-integrated mass spectrometer investigations, such as the Mars Organic Molecule Analyzer (MOMA) developed for the ExoMars rover, are readily adapted to such missions. However, for a fixed landed drilling and excavation site, the analytical approach must adapt to new variables and constraints. When analyzing samples sourced from significant depths (several km), particularly for organic detection, the drilling operation would be analogous to a sample return mission: a balance of down-hole ("in situ") triage measurements, followed by surfacing ("Earth return") of carefully encapsulated volatile-containing samples for investigation in fixed, above-ground analytical suites with multiple sample processing front-end options ("terrestrial labs"). However, the distinct advantage of the drilling scenario is that multiple samples could be available with collection priorities and analytical techniques optimized in real time, within the scope of a single mission.

We describe the value of tightly integrating multiple processing methods (e.g., liquid and gas phase capture/extraction, surface and bulk sampling, etc.) and sensor protocols in an analytical suite in a subsurface mission scenario, using a "separation mass spectrometer"-based suite concept as an example taken from flight instrument development and operation experience.